The obesity paradox – myth or reality?

Despite its sporty, outdoors reputation, Australia has the third-highest prevalence of overweight adults in the English-speaking world. The rapid rise of obesity has been blamed on the ubuquitous availability of fast food since the 1970s, more sedentary suburban lifestyles and a fall in the number of manual jobs.

Comprehensive government figures, based on the National Health Survey and Australian Health Survey, show that almost two thirds of Australians are now overweight – with a body mass index over 25. A quarter of Australians are obese, defined as a BMI over 30, and a third of people today are expected to develop type 2 diabetes during their lifetime. A host of other acute and chronic medical problems have been linked to obesity, including cancer, joint problems, sleep apnea and heart disease.

However, the small but increasingly vocal Health at Every Size movement has also claimed that the medical risks of obesity have been overblown and that social stigma and the refusal of doctors to look past obesity as a cause of disease in heavier people are to blame, rather than excess adipose tissue.

These activists often quote several studies published in recent years which appear to suggest, contrary to received medical wisdom, that people who have been diagnosed with heart conditions tend to live longer if they are overweight or obese compared to their normal weight peers. This contradictory association has been called the “obesity paradox.”

While a host of evidence based medical studies appear to prove that being overweight or obese are major contributory factors to cardiovascular deterioration, osteoarthritis, type 2 diabetes and cancer, the so called obesity paradox has been used to undermine attempts by public health authorities, doctors and health advocates to encourage at risk Australians to lose weight and get fitter.

Health advocates have observed that overweight people tend to develop heart problems at a younger age, increasing their ability to survive initial heart attacks, and that frail old people at the end of life skew the figures of weight at mortality. However the mystery of the paradox now appears to have been solved by the publication of a new study in the Jama Cardiology journal which suggests the so called paradox is produced by the misinterpretation of medical data, rather than any physical anomaly.

The study, carried out by researchers at Northwestern University in the USA, was led by Dr. Sadiya Khan, an assistant professor of medicine the University’s Feinberg School of Medicine, involved the analysis of patient data from over 190,000 in-person examinations. At the time of enrollment in the study, all participants were free of cardiovascular disease and tracking the subsequent development of the disease in afflicted individuals proved to be critical to debunking the “obesity paradox.”

There isn’t any paradox at all. People of unhealthy weight live unhealthily.

“Recent data have suggested that individuals with cardiovascular disease who are obese may live longer. But, we were able to investigate this in the greater context of healthspan and cardiovascular morbidity and shed light on this controversy by using a lifespan perspective beginning prior to the onset of cardiovascular disease. We are able to provide clear perspective of increased cardiovascular burden in overweight and obese,” Khan told ZME Science.

The data was sourced from ten major cohorts with an aggregate of 3.2 million years of follow-up between them. Over the course of these subsequent examinations, researchers assessed the number of individuals who developed coronary heart disease, stroke, and heart failure. The researchers also recorded whether fatalities among the study subjects were due to cardiovascular or non-cardiovascular reasons.

While the data showed little difference in the longevity of people of normal weight and overweight, obese individuals had significantly shorter lives than their lighter peers. The figures also revealed that overweight and obese individuals had a much higher risk of developing cardiovascular disease and spent more years living with cardiovascular disease than those of normal weight.

Not only did overweight and obese individuals have higher odds of developing a stroke, having a heart attack or heart failure, or dying from heart disease than people of normal weight, but certain cohorts of overweight people were particularly vulnerable to cardio-vascular problems.

The likelihood of having a stroke, heart attack, heart failure or cardiovascular death in overweight middle-aged men 40 to 59 years old was 21% higher than in normal weight men, for example. The odds were 32% higher in overweight women than normal weight women.

The likelihood of having a stroke, heart attack, heart failure or cardiovascular death in obese middle-aged men 40 to 59 years old was 67% higher than in normal weight men. The odds were 85 percent higher in obese women than normal weight women.

Normal weight middle-aged men also lived 1.9 years longer than obese men and six years longer than morbidly obese. Normal weight men had similar longevity to overweight men.

Normal weight middle-aged women lived 1.4 years longer than overweight women, 3.4 years longer than obese women and six years longer than morbidly obese women.

This is the first study of its size to offer a lifespan perspective on the risks of developing cardiovascular disease for normal weight, overweight, and obese individuals, rather than a relatively small snapshot of people already suffering the disease. Its findings will counter the claims of ‘fat activists’ who use the supposed obesity paradox to seed confusion and undermine people’s resolve to lose weight.

Weight control through reducing calorie intake and increasing exercise is within the grasp of every overweight individual. The problem is not that ‘diets don’t work’ but that people do not maintain the long term lifestyle changes required to reverse years of weight gain and low levels of physical activity.

“Future research needs to focus on strategies for primordial prevention to reduce the burden of cardiovascular disease in the population as a whole. We are also interested in identifying the differences in healthcare costs related to cardiovascular morbidity and mortality associated with overweight and obese,” Khan said.

Whatever the claims of HAES proponents, losing weight doesn’t only reduce the incidence of cardiovascular disease, but also other afflictions like diabetes or cancer. The truly empowering message is that almost everyone can improve their health by adopting healthier eating patterns and lifestyles, supported by appropriate public health measures.

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One Comment

Max Thomas

March 4, 2018 at 12:16 pm

There’s an abundance of evidence that increasing waist circumference is a stronger predictor of serious heart disease than body weight or body mass index (BMI). Aerobic exercise is the best type of exercise to burn belly fat, which suggests a link between lack of aerobic exercise and the risk of heart disease. Therefore, people of all shapes and sizes can benefit from a lifestyle that includes healthier eating patterns and exercise.

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